Cell Biology - Larbert High School

Cell BiologySummary Notes 2NameClassThese notes contain a summary of key facts. When revising, you will still need to refer to your jotter toremind yourself of the experimental and practical work you have done.LHS- Cell Biology Unit Summary Notes

Cells and Cell Structure Cells are the building blocks of life. All living organisms are made up of cells. Cells need to be viewed through a microscope.Plant cells and Animal cellsFungal cell e.g. yeastLHS- Cell Biology Unit Summary Notes

Bacterial CellBacteria cells do not contain any organellesplasmidCell structureFunctionNucleusContains genetic information (DNA) in animal, plant andfungal cellsPlasmidA small ring of DNA only found in bacterial cellsCell membraneControls entry and exit of substances such as oxygen andcarbon dioxide.CytoplasmLiquid inside cells containing organelles, the site of variouschemical reactionsCell WallThe outer layer of plant, fungal and bacterial cells whichhelps support the cellVacuoleMembrane bound sac that stores a solution of water found inplant and fungal cellsMitochondrionMain site of energy (ATP) production in aerobic respiration inanimal plant and fungal cellsChloroplastThe site of photosynthesis in plant cellsRibosomeSite of protein synthesis in cellsCell walls of plant, fungal and bacterial cells are not all the same. They are made ofdifferent chemicals.LHS- Cell Biology Unit Summary Notes

Enzymes Enzymes are biological catalysts.Enzymes are made by all living cells.Enzymes speed up cellular reactions and remain unchanged in the process.Enzymes are specific to their substrate.Enzymes are made from protein.Lock and KeyEnzymes fit to their specific substrate like a lock and a key. The place where an enzymebinds with its substrate is called the active site. The enzyme remains unchanged in thereaction but the substrate is changed in to the products.Enzymes can break their substrate down in to smaller products, or they can build theirsubstrates up into larger products.LHS- Cell Biology Unit Summary Notes

Enzymes and temperatureEnzyme activity can be increased with an increase in temperature. Human body enzymestend to work best at human body temperature (37oC). The temperature that an enzymeworks best at is called the optimum temperature. If an enzyme is overheated it can changethe shape of the protein. This means that the substrate will no longer fit the active site. Thismeans the enzyme has become denatured.Enzymes and ph.Enzyme activity can also be affected by pH. Most enzymes have an optimum pH aroundneutral but the stomach enzyme pepsin has an acidic optimum pH. A pH higher than theoptimum can also denature an enzyme.If enzymes are denatured, theirshape changes and this will affectthe rate of the reaction.ILHS- Cell Biology Unit Summary Notes

PhotosynthesisPhotosynthesis is the process by which green plantsmake their own food. This is a 2-stage process. Theoverall word equation for photosynthesis is:Stage 1: Light reactions The light energy from the sun is trapped by chlorophyll, in the chloroplasts and isconverted into chemical energy in the form of ATP. Water is split to produce hydrogen and oxygen. Hydrogen attaches to hydrogen acceptor molecules. Oxygen diffuses out of the leave as a waste product.Stage 2: Carbon Fixation (The Calvin Cycle) A series of enzyme-controlled reactions Uses the hydrogen and ATP created during the light reactions Carbon dioxide from the air combines with hydrogen to produce glucoseLHS- Cell Biology Unit Summary Notes

Glucose contains chemical energy which is available for use in respiration. The glucose canalso be stored as starch for future use in respiration and used to form cellulose, a chemicalin cell walls.Limiting FactorsThe rate of photosynthesis can be limited (slowed) by factors which are in short supply. Thiscauses the growth of the plant to be limited. Low light intensity can limit photosynthesis aswell as low carbon dioxide concentration and even low temperature.LHS- Cell Biology Unit Summary Notes

Respiration Respiration is a series of enzyme controlled reactions that cause the release ofchemical energy from glucose. The energy released from the breakdown of glucose is used to generate ATP bycombining ADP with an additional inorganic phosphate (Pi). The energy released from the breakdown of ATP can be used for musclecontractions, cell division, protein synthesis and nerve transmissions.Energy storedEnergy releasedThe ATP-ADP CycleEnergy fromfoodEnergy forcellular workADP PiAerobic respirationAerobic respiration is a two-step process:1. Breakdown of glucose- a glucose molecule is split in to another molecule calledpyruvate, producing 2 molecules of ATP. This takes place in the cytoplasm.2. Breakdown of pyruvate- pyruvate is broken down further in the mitochondria toproduce carbon dioxide and water. 36 ATP molecules are also generated in theLHS- Cell Biology Unit Summary Notes

second stage 38 ATP in total. The second stage can only take place in thepresence of oxygen.Anaerobic respirationIf no oxygen is available:In plants:Glucoseethanol CO2In Animals:Glucoselactic acidYeast is a fungal cell which can be used for baking and brewing because when it ferments(anaerobically respires) it produces carbon dioxide to cause dough to rise and ethanol tomake beer alcoholic.Anaerobic respiration only generates 2 molecules of ATP for every molecule of glucosebroken down.Respiration summary:cytoplasmglucosegluc2 ADP 2Piglycolysis2ATPCO2 waterpyruvatepyruvateIf oxygen is availableIf NO oxygen isavailable36 ADP 36 Pi36 ATPmitochondriaIn animalcellsIn plants yeast cellsLactic acidLHS- Cell Biology Unit Summary NotesCO2 ethanol

Cells which need a lot of energy have a high number of mitochondria e.g. muscle cells,nerve cells and sperm cells.Mitosis Mitosis is the process of cell division. Mitosis is important for growth and repair.Spindlefibreschromosomeequatorchromatids1. Chromosomes shorten, thicken and become visible. (doubled DNA)2. Chromosomes line up at the equator.3. Spindle fibres pull chromatids apart toward the poles.4. New nuclear membranes form5. Cytoplasm divides.Most cells in the body have a diploid chromosome complement. This means they have 2matching sets of chromosomes. Mitosis is important to make sure new cells also have 2complete matching sets of chromosomes.LHS- Cell Biology Unit Summary Notes

Producing Cells by Cell CultureAseptic technique: A procedure or an experiment which is carried out under sterile conditions All apparatus must be sterilised prior to using- using either chemical or heatsterilisation (autoclave) The bench surface must be disinfected using a chemical treatment Hands should be washed thoroughly and hair kept away from the sampleCell Culture Conditions:To grow cells in the laboratory you must provide the correct conditions: Suitable growth media containing all the nutrients required by the cell to grow e.g.amino acids, salts, water etc. Suitable temperature i.e. 30oC (for bacteria) or 37oC (for human cells) Source of oxygen Sterile conditions to prevent contamination with unwanted microorganismsLHS- Cell Biology Unit Summary Notes

Transport across the cell membraneThe cell membrane The cell membrane is made of lipids and proteins and is selectively permeablePassive transport does not require energy and moves molecules along a concentrationgradient. There are 2 types of passive transport in cells:Diffusion the movement of substances from a high concentration to a low concentration downa concentration gradient.Oxygen, carbon dioxide and glucose can travel bydiffusion. Diffusion is important because cells can gain raw materials (eg glucose andoxygen) and remove waste products (eg CO2).Osmosis the movement of water molecules from an area of high water concentration to anarea of lower water concentration through a selectively permeable membrane.Plants receive water into their roots by osmosis.LHS- Cell Biology Unit Summary Notes

A plant cell placed in pure water will swell and become turgid as it fills with water. A plantcell placed in a strong salt solution will lose water by osmosis and so become plasmolysed.An animal cell placed in pure water would gain water by osmosis and eventually burst,having no cell wall to prevent it. An animal cell placed in a strong salt solution will losewater by osmosis and shrivel up.Active Transport a process that moves molecules against a concentration gradient and so requiresenergy in the form of ATP. Nerve cells carry out active transport to maintain highconcentrations of different ions (eg sodium and potassium ions) inside the cellcompared with outside the cell.LHS- Cell Biology Unit Summary Notes

DNA and protein synthesis DNA is the code for making proteins. DNA is a large molecule contained inside the nucleus of a cell. Genes are made up of DNA. Each gene is a code for a different protein. DNA is a double stranded helix made up of four bases – A, T, G and C. A always pairs with T and C always pairs with G- these are complimentary base pairs. Each triplet of DNA bases codes for 1 specific amino acid The sequence of DNA bases determines the amino acid sequence in the protein.DNA is too large to move outside of the nucleus to carry the genetic code to a ribosome (forprotein synthesis). So another type of molecule called messenger RNA is needed. (mRNA).DNARNADouble strandedSingle strandedA pairs with TA pairs with UMessenger RNA copies the code of DNA inside a nucleus then carries this code out to aribosome where the base sequence determines the amino sequence of the newly formedprotein. Amino acids are held together by peptide bonds.The variety of protein shapes and functions depends on eachindividual sequence of amino acids.Type of ProteinEnzymeHormonesAntibodiesFigure 1: Double helixstructure of DNA- heldtogether by complimentarybase pairs.StructuralproteinsLHS- Cell Biology Unit Summary NotesFunctionSpeed up chemical reactionsChemical messengers which travel through theblood to their target organProduced by your immune system to fightdisease (found in your blood)Like hair/skin/nails- protect various parts of thebody

Genetic EngineeringHuman genes can be inserted into a bacterial cell plasmid. This causes the bacterial cell tomake the human protein. This process can be used to make insulin for treatment ofdiabetes.plasmid1. Section of DNA containing required gene from human chromosome is identified.2. This gene is extracted.3. Plasmid is extracted from bacteria cell and human gene inserted into it.4. Modified plasmid (containing human gene) is inserted back into bacterial cell.5. Transformed bacterial cells are grown in fermenters and desired product i.e. insulin isproduced.6. Product i.e. insulin is purified before use as a treatment.LHS- Cell Biology Unit Summary Notes

Self Assessment Check-list:What are the areas you know and understand well? Whichsections do you need to revise again, in a different way? Are there any areas you needfurther help with to understand?Key AreaSection1. Cell StructureStructures and their functions2. Transport acrossStructure of membranethe membraneDiffusionOsmosisActive transport3. Producing NewPurpose of mitosisCellsStages of mitosisCell culture and aseptic technique4. DNA and theproduction ofproteinsStructure of DNARole of mRNA in making protein5. Proteins andVariety and function of proteinsEnzymesProperties of enzymesConditions that affect enzymes6. Genetic EngineeringStages of genetic engineering7. PhotosynthesisLight ReactionsCarbon FixationFates of glucoseLimiting Factors8. RespirationAerobicRespirationBreakdown ofglucoseBreakdown ofpyruvateAnaerobic RespirationLHS- Cell Biology Unit Summary Notes